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THE AMEBIC AN NATURALIST [Vol. XL VII 



rations of brother X sister breeding, it is extremely im- 

 probable that any effect will be produced by a further 

 continuation of the same method of breeding. If an 

 apparent effect should suddenly appear some time later 

 than the tenth generation the case would need the most 

 critical scrutiny, to determine whether the observed effect 

 had really been due to the inbreeding, rather than to some 

 other unsuspected cause. 



The values of the Z's in Table I are maxima: No par- 

 ticular coefficient of inbreeding can have a higher value 

 than that given in the table. It is not possible, for ex- 

 ample, so to breed any animal (having an obligate 

 bisexual type of reproduction) that its pedigree on analy- 

 sis will give Z z > 87.5. If, therefore, the coefficients of 

 Table I are plotted the result will be the maximum limit- 

 ing curve of inbreeding. This curve is shown in Fig. 1. 



In all actually realized pedigrees except those in which 

 there has been continued brother X sister breeding the 

 curve of inbreeding found will lie wholly or in part below 

 the maximum curve shown in Fig. 1. 



